Kate Moss once said that nothing tastes as good as skinny feels. That’s a lie. Just consider: dulce de leche ice cream. A fresh lobster roll. Tropical jelly beans. I enjoyed all these indulgences and more while pregnant with my second child—and gained around 60 pounds. Whoops. I don’t regret a bite, but I do have my pride, and about four months after delivering a baby girl by C-section, that pride was seriously wounded.

Here’s what happened: My mom, Michelle, came to visit and suggested we take a walk. Specifically, a speed walk, her exercise of choice for three decades. We laced up and set out toward the bike path near my house, and about five minutes in, I started panting.

Ten minutes in, I pretended to scratch my ankle because I just needed to breathe. My mom is 68. I am 37. But at that moment, our ages might as well have been reversed. And as tempting as it is to blame my postpartum condition, the truth is I was out of shape long before I got pregnant.

That is a fact I’ve tried to ignore, but my job interviewing celebs shoves it in my face. Over the years, I’ve talked to dozens of stars about their diet and exercise habits. Helpful: Fergie, who recommended that busty ladies like myself wear two sports bras to jump rope because "there’s a lot of waving." Not as helpful: Jennifer Aniston, who, when asked about her favorite and least favorite workouts, answered: "I love them all. I love working out." And Blake Lively once sheepishly told me she didn’t have to exercise or watch what she ate because she’s “lucky.”

Kate Hudson vs. mom

This past summer, I interviewed Kate Hudson, and she showed me how to use MyFitnessPal, that app that tracks your daily calorie intake and physical activity. That’s when it occurred to me: My mom could be my own fitness pal! She’s better than an app because (a) we have the same body type, so presumably what works for her would work for me, and (b) unlike an app, I couldn’t just delete her off my phone when I wanted to give up.

My mom lives in Miami, and I live in Massachusetts, but the miles wouldn’t matter if we checked in daily (and we did). She would hold me accountable. Compared with stars, most of us don’t have the luxury of hiring trainers or nutritionists (or, in the case of Kim Kardashian, a professional spray tanner named Jimmy Coco who makes house calls). But the funny thing is, my mom might have a healthier lifestyle than most of them because it is an enduring one. No diets, no fads. And, until recently, no apps.

Mall walking? Check!

Mom has been speed-walking for as long as I can remember. As I type, she is probably sporting her white visor and lunging to keep up with her striding, nearly 6-foot-tall walking partner, Cathy. Almost every day, they rise with the sun and walk the same route—to the local outdoor mall, around and back—averaging about 4 1⁄2 miles; it takes just over an hour.

I can just see them now: elbows flapping, hips sashaying. "Don’t make me sound ridiculous," says Mom. "I don’t wear a velour tracksuit. Or do that thing with my arms." (Actually, she kind of does.) The overall effect is that they look like they are rushing to the nearest restroom, and chances are good that they are: They often stop at Bloomingdale’s for a quick pee break.

Is it technically speed-walking? Maybe not: “Race walking” is an Olympic sport requiring one foot to be in contact with the ground while the supporting leg is kept straight. It dates back to at least 18th-century England, when tall men with long strides dominated. But in the 1960s, a Polish guy named Jerzy Hausleber discovered that short athletes could have a leg up on their taller competitors, if they wiggled their pelvises a certain way. In other words, Hausleber might have seen potential in my mom, who is 5 feet and change, as opposed to her friend Cathy.

Anyway, Mom and I worked out a plan. I would eat and exercise like her for a month, updating her on my progress (or lack thereof). I ordered a digital scale, and on day one, I recorded my weight at 155 pounds (constant nursing had helped me, but I still had 25 pounds to go).

Tuna-egg salad, no can do

The eating part would be pretty straightforward. "I have a philosophy that translates into a strategy about everything I eat," says Mom. "I read about it in a magazine: three-quarters plants, one-quarter everything else." On a typical day, she has two slices of lightly buttered multigrain toast for breakfast, fruit with a cup of zero-fat yogurt or cottage cheese for lunch (as an alternative, she sometimes makes smoothies) and a small portion of chicken or fish with salad and steamed vegetables for dinner.

Simple enough, though I made a couple of adjustments, such as swapping out the bread for hearty granola for breakfast and occasionally making an arugula and avocado salad for lunch. I especially needed more sustenance in the morning, as I confessed to my journal on day two: "I am nursing & hungry!" (Plus, Mom, buttered toast doesn’t exactly fit the "three- quarters plants" theory.)

For dinner, I briefly considered making Mom’s tuna fish recipe—she mixes in chopped celery and hard-boiled egg in a huge storage dish—but decided against it. I have OD’d on that salad too many times.

I felt a similar aversion to her smoothie recipe. Along with her fruit, yogurt, almond milk and medley of Christmasy spices, Mom drops a “tiny little cookie” into the blender before pressing "liquefy." "It’s divine," she says of this addition, usually a Trader Joe’s gingersnap. Personally, I prefer my cookies in solid form.

Adventure: on

The exercise part required more planning. First step: buying a fanny pack (the horror!). Second step: locating my never-been-used-before Asics sneakers. "Are those your adventure shoes?" my 4-year-old son asked upon seeing their debut. Third step: Finding a walking partner. I posted an invitation on Facebook, and my friend Beth’s husband, Ryan, wrote back. We started the next morning—laps around the Smith College track field. The hardest challenge was making the time to walk with two kids at home. My husband, Addie, took care of all the morning chores, except for breast-feeding, so that I could meet Ryan at 8 a.m. Using the app Steps, we aimed to reach 8,000 to 9,000 steps an outing.

Aside from my mom, Addie was my biggest cheerleader; while their encouragement helped, it was best given one-on-one. Halfway through the challenge, my mom visited, and we went for a walk. When my husband told her to make me "work hard," I controlled the urge to throw my sneakers at him and then hate-eat a pizza. "Felt a murderous rage," I scribbled in my journal. "Pressure doesn’t work."

But accountability does. I wasn’t just checking in with my mom on a daily basis; I was checking in with myself, observing my habits and tweaking them when necessary. And to my amazement, the pounds came off—about 2 a week. Eating less was hard, but I enjoyed what I ate: garden-fresh gazpacho, fish, fruit mixed with cottage cheese (surprisingly delicious). I snacked on apples and peanut butter, almonds and spicy pepitas.

The verdict

I loved beginning each day with a brisk walk to clear my head. I also started swimming for the first time in years. I’ve always thought of sweltering hot days as great “ice cream days.” But they’re also great “lake days.”

“Feeling good & strong,” I wrote after one particularly refreshing dip. My bathing suit no longer feels like sausage casing.

More than a month has passed, and the morning walking, while enjoyable, hasn’t been sustainable. I just have too many obligations in the a.m. But I made a pact with myself to walk every day, and I’ve been honoring it. It doesn’t matter whether it’s a late-morning stroll with my daughter or a solo pre-dinner jaunt to pick up a bottle of rosé—just as long as I go.

As for Mom’s eating plan, I have stuck with it. When I vacationed with my in-laws in the Adirondacks, it took great willpower not to scarf down s’mores. I did have two rectangles of a chocolate bar, because that’s what Mom would do.

As of today, I have lost 15 pounds since I started the challenge, but more importantly, I have gained better habits. Next time Mom wants to go for a walk, I won’t be so far behind.